This invention relates to fuel dispensing systems and, more particularly, it concerns a liquid shutoff safety device for use with a filter and impact valve arrangement in a remote pump type fuel dispensing system.
As is well known in the fuel dispensing art and as shown, for example, in FIG. 1 of the drawings, each fuel inlet 10 of a conventional remote pump type fuel dispenser usually has mounted thereabove a fuel filtering assembly 12 including, for example, a horizontally oriented, disposable filter 14, for removing suspended particles from the incoming fuel F supplied to the dispenser by, for example, a sump pump in a large supply tank. The filters 14 need to be replaced on a regular basis in order to facilitate proper filtering and to maximize fuel flow rate. Since the filters are changed regularly and since the liquids being dispensed are hazardous, it is important to prevent fluid flow from the filter attachment point during filter replacement not only from the standpoint of system operator safety, but also out of concern for the environment.
The fuel dispenser is customarily installed at a dispensing site with an impact valve 16 (FIG. 1) located below each supply inlet 10. The impact valve 16 is of conventional design and incorporates an internal spring which biases the valve closed to stop the flow of fuel to the dispenser in case of an emergency. In particular, the impact valve 16 includes a releasable latching arrangement made up in part by a latch arm 18 having one end pivotally attached to the upper neck of the impact valve by a bolt 20 (FIG. 3) and including a rectangular notch 22 near the other free end 24. The notch 22 cooperates with a stud 26 extending from a valve actuating arm 28 which is mounted in a conventional fashion so as to rotate along with a rectangular valve shaft 30.
When the stud 26 of the value actuating arm 28 is seated in the notch 22 of the latch arm 18 as shown in FIG. 1, the impact valve is held open against the bias of the internal spring. If, however, the latch arm is tripped, that is if the latch arm 18 is moved down away from the stud 26 of the valve actuating arm 28 (FIG. 3), then the stud 26 is freed from the notch 22 and the valve actuating arm 28 and valve shaft 30 are allowed to rotate in a clockwise direction under the bias of the internal spring and the impact valve closes.
The latch arm 18 can be manually tripped, for example, by a system operator in order to stop the flow of fluid to the filter 14 prior to removal of the filter during filter replacement. Even though the remote pump, for instance, a sump pump in a fuel storage tank of the fuel dispensing system may be turned off, it is customary practice to close the impact valve 16 prior to removal of the filter 14 to make sure that fluid flow to the filter attachment point is stopped and, thereby, reduce the chances of undesirable or inadvertent leakage of fluid from the system.
Alternatively, the latch arm 18 may be automatically tripped, for example, if the fuel dispenser were to receive a shock or blow, such as if it were struck by an automobile. Additionally, the conventional impact valve 16 includes an annular, v-shaped notch 32 which serves as a shear point if, for example, the fuel dispenser were to be impacted severely and knocked over. The shear notch 32 is located between the latch arm pivot 20 (FIG. 3) and the valve shaft 30 so that in the event that the impact valve is sheared in two the latch arm 18 would be pulled away from the stud 26 of the valve actuating arm 28 and, as such, allow the impact valve to close.
As disclosed, for example, in U.S. Pat. No. 4,818,397 issued on Apr. 4, 1909, complicated liquid shutoff valve arrangements have been developed for automatically stopping fluid flow to a filter upon filter removal in an effort to reduce leakage during filter replacement by not having to rely upon a system operator to manually close a valve prior to removing the filter. Such complicated valve arrangements increase unit cost and are subject to failure due to an increase in the number of moving parts.
In light of the foregoing, there exists a need for an improved liquid shutoff device which will ensure that the fluid flow to a filter is automatically stopped prior to filter removal.